There are an estimated 1.1 billion Hindus worldwide, making Hinduism the third largest religion (after Christianity and Islam). About 80 percent of India's population identify as Hindus and 30 million more Hindus live outside of India. Nepal is majority Hindu and there are many Hindus in Bangladesh as well. Hindus make up about 2% of the population in the UK and less than 1% in the USA.
Hinduism (from Persian hindu, Sanskrit sindhu, "river", specifically the Indus River) is a broad term referring to the indigenous religion(s) of the Indian subcontinent. Like other indigenous religions, Hinduism has no founder or date of origin and its early history is little known. It is the product of religious development in India that spans nearly 4,000 years, making it perhaps the oldest surviving world religion.
Hinduism encompasses a wide variety of traditions, which are closely related and share common themes but do not constitute a unified set of beliefs or practices. Hinduism is not a homogeneous, organized system. Many Hindus are devoted followers of Shiva or Vishnu, while others look inward to the divine Self (atman). But most recognize the existence of Brahman, the unifying principle and Supreme Reality behind all that is.
Most Hindus respect the authority of the Vedas (the oldest sacred texts) and the Brahmans (the priestly class), but some reject one of both of these authorities. Hindu religious life might take the form of devotion to God or gods, the duties of family life, or concentrated meditation. Given all this diversity, it is important to take care when generalizing about "Hinduism" or "Hindu beliefs."
The first sacred writings of Hinduism, which date from about 1500-1200 BCE, were primarily concerned with the ritual sacrifices associated with numerous gods who represented forces of nature. A more philosophical focus began to develop around 700 BCE, with the Upanishads and development of the Vedanta philosophy. Around 500 BCE, several new belief systems sprouted from Hinduism, most significantly Buddhism and Jainism.
In the 20th century, Hinduism began to gain popularity in the West. Its different worldview and tolerance for diversity in belief made it an attractive alternative to traditional Western religion. Although there are relatively few western converts to Hinduism specifically, Hindu thought has influenced the West indirectly by way of religious movements like Hare Krishna and the New Age, and even more so through the incorporation of Indian beliefs and practices (such as the chakra system and yoga) into health and spirituality.